Burners for burning a pulverulent fuel are known. They supply the boiler with a pulverulent fuel and air or some other oxygen-containing gas or oxygen in order to burn the pulverulent fuel, in particular pulverized coal, and, in the process, to generate heat. To ignite such burners, ignition torches are provided. The ignition torches can be embodied as separate ignition torches or as integral ignition torches forming a unit with the pulverized coal burner. To produce the ignition flame, the ignition torch is usually supplied with a gaseous or liquid fuel.
The disadvantage with such known burners is the demand for fuels, usually fossil fuels, to produce the ignition flame. The carbon dioxide emissions of such burners are generally high and, owing to the rising trend in oil and gas prices, burners of this kind are becoming increasingly uneconomical to operate.
As an alternative to gas- or oil-fueled ignition torches, there have also been attempts to ignite the pulverulent fuel supplied via the burner at electrically heated surfaces of the burner. Most recently, plasma ignition torches have furthermore been developed, said torches using a plasma flame as a source of ignition for the burner. In contrast to oil or gas flames, the plasma flame is significantly shorter and hotter. The advantage in using plasma flames is that the ignition torch does not require fossil fuels.
A pulverized coal burner with an integrated plasma ignition torch is known from EP 2 253 884 A1, for example. The pulverized coal burner has a fuel duct, via which the pulverized coal can be passed through the burner. The fuel duct is substantially cylindrical. There is also a flow of air through said fuel duct. A plasma ignition torch is arranged centrally along the burner center line in the fuel duct. The pulverized coal/air mixture is ignited in the pulverized coal burner and is then discharged at the burner outlet.
U.S. Pat. No. 5,689,949 and U.S. Pat. No. 5,845,480 describe burners with a plasma ignition device. Within the burner, a fuel/air mixture is introduced into a chamber and is ignited there by a plasma ignition device arranged on the chamber wall.
In the burner known from U.S. Pat. No. 5,156,100 A, the fuel is divided into a main flow and an additional flow. The additional flow is ignited with the aid of a plasma ignition torch and is then mixed with the main flow of fuel, thereby igniting the latter as well.
Starting from the various known burners with an integrated plasma ignition torch, one object of the present invention can be considered to be that of providing a pulverized coal burner in which the outlay on maintenance and testing is low and which prevents backfires into the supply line for the pulverulent fuel.